I consider this far better than any other German crime series I have watched lately - and I'm doing so quite regularly.
Other than (modern) Tatort and most other newer German crime series, Letzte Spur Berlin is not trying to have more and more fancy and odd cases. Neither is it trying to be funny or hyper-ethical. Here the crimes do not occur while the inspectors happen to be around (as in many Tatorts), nor are they trying to show the daily struggles of being a transvestite. And last but not least there are no dramatic scenes in which the inspectors heroically save victims or convince criminals of the wrongness of their doing in a heart-melting speech.
Instead there are down-to-earth cases that seem realistic and convincing. Also, things can go wrong and there is not always a happy ending.
I would not call this show perfect, it is not. But looking at the recent quality of major German crime-series this one really stands out by far! (I have only seen some episodes as I cannot find it anywhere to buy and am not regularly watching TV)